The present invention relates to broadcast transmission systems and is particularly directed to compensation of distortion within a digital transmission system, such as a digital TV (xe2x80x9cDTVxe2x80x9d) transmission system.
A high-speed broadcast transmission system such as a DTV broadcast system includes components that distort an information signal away from intended values. Specifically, the system includes a power amplifier that imposes non-linear distortion upon the signal, as a signal is amplified. Also, the broadcast transmission system includes filters, such as band-limiting filters, that impose linear distortion upon the information signal as the signal is filtered.
As a result of such distortions within the transmission system, instantaneous amplitude variations (AM/AM) and instantaneous phase variations (AM/PM) occur. In addition, frequency dependent amplitude and phase variations occur. It is to be appreciated that within a phase-amplitude modulated system, integrity of amplitude and phase must be preserved for optimum system performance.
There is a need for a high-speed technique for adaptive correction of linear an non-linear distortion within a digital broadcast transmission system.
In accordance with one aspect, the present invention provides a digital broadcast transmission system. The system includes a signal provision means for providing an electrical information-conveying signal. Antenna means emits a broadcast signal that contains the contents of the information signal. Amplifier means amplifies the information signal to a power level suitable to excite the antenna means to emit the broadcast signal. The amplifier means causes non-linear distortion to the information signal. Signal processing means processes the information signal. The signal processing means causes linear distortion to the information signal. A single filter pre-distorts the information signal to compensate for the linear and non-linear distortions.
In accordance with another aspect, the present invention provides a digital broadcast system that includes signal provision means or providing an electrical information-conveying signal along a signal stream. Antenna means, located the end of the signal stream, emits a broadcast signal that conveys the contents of the information signal. A plurality of components is located along the signal stream between the signal provision means and the antenna means. The plurality of components causes distortion to the information signal. At least one of the plurality of components causes linear distortion to the information signal and at least one of the plurality of components causes non-linear distortion to the information signal. A single filter pre-distorts the information signal to compensate for all of the distortion caused by the plurality of components.